The present invention generally relates to electrochromic devices and devices incorporating electrochromic elements, such as devices incorporating both electrochromic elements and optical sensors.
Variable transmittance light filters, such as electrochromic light filters, have been proposed for many uses including in architectural windows; skylights; rearview mirrors, windows, and sunroofs for automobiles; and in certain imaging systems. Such electrochromic light filters respond to a change in applied voltage by changing their transmittance. In general, it has been a goal of designers of electrochromic elements to configure the elements to vary transmittance uniformly across the whole element.
As noted above, electrochromic elements have been employed as light filters in imaging systems such as cameras. Examples of cameras utilizing electrochromic light filters are disclosed in U.S. Pat. Nos. 5,555,069, 5,387,958, 4,554,587, and 4,256,372. In each of these patents, the electrochrornic light filter is spaced apart from the image recorder (i.e., the film or image sensor array) and exhibits substantially uniform transmittance levels. Such electrochromic light filters are used in combination with the mechanical irises that are commonly used in cameras to vary the exposure level of the film or image sensor array. Such conventional mechanical irises are either hand operated or operated by a motor in response to the detected illumination of the scene or object to be imaged. Although the electrochromic light filters can vary the exposure level of the image recorder, a conventional mechanical iris is required if the camera is to allow for the depth of field of the image to be adjusted.
Integrated circuit optical sensors are increasingly used to provide visual input for control systems as well as in cameras. Many applications place optical sensors in harsh environments, requiring that the sensors be enclosed in a protective package. Presently, commercial optical sensor packages are developed from conventional semiconductor packages incorporating clear plastic or add-on windows to conventional molded or ceramic devices including a lead frame. An example of such a device is disclosed in U.S. Pat. No. 5,861,654. These packaging assemblies are expensive and difficult to manufacture.
An optical sensor may be used in applications exposing the sensor to a range of light intensities beyond the dynamic range of the sensor. As an example, a configuration allowing the sensor to operate at low light levels may cause the sensor to wash out at a high light level. As another example, consider a scene illuminated by fluorescent lighting, which cycles in intensity with the alternating current supply. A pixel array sensor with a high scan rate will have portions of each frame illuminated by varying levels of light. To avoid this problem, an integration period of at least approximately 30 milliseconds must be used. Since the scan time is generally a multiple of the integration time, a camera set to 30 milliseconds scan period for a bright scene may result in an excessively long scan time for a dim scene. Further, particularly if a lens is used to focus light on the sensor, direct exposure to sunlight can generate sufficient heat to damage sensor elements. Applications where a camera or image sensor is likely to be exposed to sunlight for long periods of time include automotive headlight control systems such as that disclosed in commonly assigned U.S. patent application No. 09/528,389, entitled xe2x80x9cIMPROVED VEHICLE LAMP CONTROL,xe2x80x9d and filed on Mar. 20, 2000; automotive moisture sensing systems such as that disclosed in commonly-assigned U.S. Pat. No. 5,923,027; and in automotive electronic vision systems such as those disclosed in commonly-assigned U.S. patent application No. 09/001,855, entitled xe2x80x9cVEHICLE VISION SYSTEM,xe2x80x9d and filed on Dec. 31, 1997, now abandoned and commonly-assigned U.S. patent application No. 09/153,654, entitled xe2x80x9cSYSTEMS AND COMPONENTS FOR ENHANCING REAR VISION FROM A VEHICLE,xe2x80x9d and filed on Sep. 15, 1998, now U.S. Pat. No. 6,550,949. The disclosures of the above-noted patent and patent applications are incorporated herein by reference.
Mechanical and electromechanical shutters, when used, are not typically part of the optical sensor package. Electrically attenuated grayscale filters are never part of the commercial sensor device package, if available at all.
What is needed is a package for protecting an optical sensor that is inexpensive, compact, and easy to manufacture. The package should be adaptable to include an electronically controlled electrochromic variable attenuator.
An aspect of the present invention is to provide a structure enabling an electrochromic device to be readily mounted to a circuit board. To achieve this and other aspects and advantages, an electrochromic device of the present invention comprises a first substrate, an electrochromic medium disposed on the first substrate, a pair of electrodes in contact with the electrochromic medium, a pair of conductive clips, each in electrical contact with a respective one of the electrodes, and two pairs of electrical lead posts for mounting the first substrate to a circuit board, where each pair of lead posts is attached to, and extends from, a respective one of the conductive clips. According to another embodiment of the present invention, a device is provided that comprises an electrochromic element having a transmittance that varies in response to an electrical signal, a base substrate disposed in spaced relation to the electrochromic element, a seal disposed between the base substrate and the electrochromic element, such that the seal, base substrate, and electrochromic element form a sealed cavity therebetween. The device further comprises an optical sensor disposed on the base substrate within the sealed cavity.
Another aspect of the present invention is to provide an imaging device that does not require a mechanical iris. To achieve this and other aspects of the present invention, an imaging device of the present invention comprises an image recorder for recording a scene or object and an electrochromic element positioned between the image recorder and the object or scene to be imaged. The electrochromic element is configured to exhibit a non-uniform transmittance in response to an applied electrical signal.
It is an aspect of the present invention to provide a package for an optical sensor that is inexpensive and easy to manufacture. Another aspect of the present invention is to provide a package for an optical sensor that incorporates an electrically controlled variable attenuator. A further aspect of the present invention is to provide a method for encapsulating an optical sensor.
To achieve the above aspects and other aspects and features of the present invention, a package for encapsulating an integrated circuit optical sensor is described. The package is mountable on a support substrate. The sensor has a bottom surface and a top surface, the top surface comprising imaging electronics connected to a plurality of sensor bonding pads. The sensor bonding pads provide bonding points for connections off the sensor. The package includes a base substrate with a top surface and a bottom surface. The base substrate is constructed of an insulating material. The base substrate top surface has the optical sensor bottom surface bonded thereon. Conductive strips on the base substrate top surface extend from a region near the optical sensor to an edge of the base substrate top surface. Wires are bonded on one end to a sensor bonding pad for which connection is desired and on the other end to a corresponding conductive strip. A window is bonded to the base substrate top surface in a spaced-apart relationship by a seal material. The window admits light to the optical sensor. A means for connecting each conductive strip to a corresponding trace on the support substrate is also provided. The seal material extends around the sensor enclosing each wire but not enclosing any of the connecting means.
In one embodiment, the means for connecting each conductive strip to the corresponding trace on the support substrate includes a plurality of conductive clips, each clip having a connecting section, an opposing section, and at least one joining section joining the connecting section and the opposing section. The connecting section and the opposing section are separated by a distance less than the thickness of the base substrate. Each clip is placed on the base substrate such that the connecting section is in contact with one conductive strip and the opposing section is in contact with the base substrate bottom surface. In one refinement, the support substrate is a through-hole printed circuit board. Clips include a lead allowing the package to be mounted to the through-hole printed circuit board. In another refinement, the support substrate is a flexible circuit and each clip can be attached to the flexible circuit. In yet another refinement, clips can be surface mounted to the support substrate.
In another embodiment, the support substrate defines an opening of sufficient size to accept the window without accepting the entire base substrate. The means for connecting each conductive strip to a corresponding trace on the support substrate has conductive strips formed to provide clipless bonding points to corresponding traces on the support substrate bottom surface. The at least one conductive strip is positioned such that, when the at least one conductive strip is bonded to the corresponding trace, the window is inside the opening.
In still another embodiment, a cavity is formed by the base substrate, the window, and the seal material bonding the window and the base substrate. The cavity is filled with an optically transparent material. This material may be a transparent curable resin.
In yet another embodiment, the window is a first window. The package further includes a first transparent electrode on the top surface of the first window. A second window is bonded to the first window in a spaced-apart relationship by a seal material. The second window bottom surface has a second transparent electrode thereon. The first window, second window, and seal material bonding the second window to the first window form a cavity containing an electrochromic medium of variable transmittance. An electrochromic variable attenuator is formed by the first transparent electrode, the second transparent electrode, and the electrochromic medium, the electrochromic variable attenuator able to regulate the intensity of light admitted to the optical sensor.
In other embodiments, the window is coated with a film operative to affect the spectrum of light passing through the window and striking the optical sensor. Electro-optic and photochromic filters may be attached to the window. One or more lenses may be attached to the window or the window may be formed to function as one or more lenses.
A method for making the package is also provided. The method includes forming a base substrate from a nonconductive material. Conducting strips are deposited on the base substrate top surface, each strip extending from the region onto which the sensor will be attached to an edge of the base substrate top surface. The bottom surface of the sensor is adhered to the base substrate top surface. Wires are bonded between each sensor bonding pad and a corresponding conducting strip. A window is bonded to the base substrate top surface in a spaced-apart relationship using a seal material. The seal material encloses each wire but does not touch an edge of the base substrate top surface.
In one embodiment, the window is one substrate of an electrochromic variable attenuator.
In another embodiment, wherein the window is a first window, the method further includes depositing a first transparent electrode on the first window top surface. A second window is formed from a nonopaque material, the second window having a bottom surface with a second transparent electrode deposited thereon. The second window is bonded to the first window in a spaced-apart relationship using a seal material. A cavity is formed by the first window, the second window, and the seal material bonding the second window to the first window. At least one opening is formed in the cavity and the cavity is filled with an electrochromic medium. The opening is sealed. Electrical connections are attached to the first transparent electrode and the second transparent electrode.
Another package is provided for sensors with bonding pads capable of providing flip chip bonding points. The package includes a base substrate constructed of an insulating material. Conductive strips are on the base substrate bottom surface. The optical sensor top surface is flip chip bonded on the base substrate bottom surface such that each sensor bonding pad is connected to a corresponding conductive strip, each conductive strip extending to the edge of the base substrate. A means for connecting each conductive strip to a corresponding trace on the support substrate is also provided.
In one embodiment, the base substrate is transparent, admitting light to the imaging electronics.
In another embodiment, the base substrate is opaque. A hole in the base substrate permits the optical sensor imaging electronics to receive light. The package further includes a window bonded to the base substrate top surface in a spaced-apart relationship by a seal material. The seal material extends around the hole. The window therefore admits light to sensor imaging electronics.
In yet another embodiment, a cover is bonded to the base substrate bottom surface by a seal material in a spaced-apart relationship.
In a further embodiment, the optical sensor is coated with a transparent curable resin to provide environmental protection.
A method for making the package is also provided. The method includes forming a base substrate from a nonconductive material. Conducting strips are deposited on the base substrate bottom surface, each strip extending from the region onto which the sensor will be attached to an edge of the base substrate bottom surface. The sensor top surface is flip chip bonded to the base substrate bottom surface such that each sensor bonding pad is connected to a corresponding conductive strip.
An optical sensor with controlled light attenuation is also provided. The sensor includes an optical sensor assembly having an integrated circuit optical sensor disposed within a package, the package including a package window through which light strikes imaging electronics. A variable attenuator is bonded to the package surface in a spaced-apart relationship using a seal material extending around the package window.